In a laser scanner, a light beam generated by a laser periodically sweeps over a monitored zone with the help of a deflection unit. The light is remitted at objects in the monitored zone and is evaluated in the scanner. A conclusion is drawn on the angular location of the object from the angular position of the deflection unit and additionally on the distance of the object from the laser scanner from the time of flight while using the speed of light. The location of an object in the monitored zone is detected in two-dimensional polar coordinates using the angular data and the distance data. The positions of objects can thus be determined or their contour can be determined.
Laser scanners are used in safety technology for monitoring a danger source, such as a dangerous machine. Such a safety laser scanner is known from DE 43 40 756 A1. In this process, a protected field is monitored which may not be entered by operators during the operation of the machine. If the laser scanner recognizes an unauthorized intrusion into the protected field, for instance a leg of an operator, it triggers an emergency stop of the machine. Other intrusions into the protected field, for example by static machine parts, can be taught as permitted in advance.
Safety laser scanners have to work particularly reliably and must therefore satisfy high safety demands, for example the EN13849 standard for safety of machinery and the machinery standard EN1496 for electrosensitive protective equipment (ESPE). To satisfy these safety standards, a series of measures have to be taken such as a secure electronic evaluation by redundant, diverse electronics, functional monitoring or special monitoring of the contamination of optical components, in particular of a front lens.
A generalization of a protected field also for applications outside safety technology, for instance for automation technology, is called a detection field here. Detection fields are virtually defined part regions of the monitored zone of the laser scanner that are typically configured at the time of installation and evaluated at the run-time. The detection fields lay down which regions of the detected scenery are to be evaluated with respect to objects, with this possibly only relating to a specific time in each case and with the definition of the detection fields changing at a different time. The type of detection field determines which type of evaluation is to be carried out and which response an object intrusion into a detection field triggers. With the already addressed protected fields, an object intrusion results in a safety-directed shutdown. Warning fields are mostly disposed in front of protected fields and trigger an alarm without directly intervening in the system and should as a rule prevent a continuing intrusion into a protected field still in good time by the alarm. Automation fields are the general complementary term to protected fields and warning fields, that is they are not safety-directed, but are rather used, for example in the form of a functional field as a virtual switch, as a measurement field for determining volumes or for other measurements.
The configuration of detection fields, above all in the case of safety-related protected fields, is essential for a proper function of the laser scanner. Relatively few aids are nevertheless currently provided for the user. An input of the boundaries of the detection field typically takes place in the laser scanner or in configuration software. In this respect, the dimensions of the detection field have to be known and there is no feedback in the actual scenery except for laborious testing using a test bar. It is admittedly also known to mark the protected fields by adhesive tapes or by color surfaces. However, this does not excuse the user from providing that the regions thus marked are actually configured as detection fields in the laser scanner.
A laser scanner is inter alia known from DE 20 2009 012 589 U1 that transmits a visible light beam in the direction of an object detected in a protected zone. The check of the configured protected fields is thus facilitated; however, only a spot test is still respectively possible and there is no overall overview.
U.S. Pat. No. 8,638,446 discloses a laser scanner having an integrated projector that is able to project visible information onto an object located in the environment. This information includes, for example, images, CAD files or point clouds from scanner measurements. For example, a texture is thus projected over an object or over a virtual object in a planned or ideal configuration over the actual object. Neither a securing with the aid of protected fields nor a visualization of detection fields is provided.
US 2005/0052720 A1 deals with a laser projection system in which a laser beam can be guided in two dimensions with the aid of two rotating deflection mirrors arranged perpendicular with respect to one another. There is, however, no connection with laser scanners.